Neither Demidov or Perfetti for that matter are "below average".
Focusing on Demidov though......
Edgework + Acceleration
Edgework + Vision
Edgwork + Deceptiveness
Some breakout speed + strength
Elite edgework
Another view....
Strength
My opinion....with supporting videos from just the past week. He is far from a below average skater. Is he a burner? I don't think he is that. Does he have dynamic edges, with which he can control the puck, create time and space, and position himself in prime positions....oh hell yeah. His skating may seem unorthodox to some, but he is not below average. Lateral movement is well above average in my opinion. The jury is still out on straight line speed.